Embodiments relate to a light emitting device, a light emitting device package, and a lighting system.
In light emitting devices, P-N junction diodes having the properties of converting electrical energy into light energy may be formed by combining group III and V elements on the periodic table. Light emitting devices may realize various colors by controlling the composition ratio of compound semiconductors.
A white LED may be realized by mixing R, G, B independent light sources with each other or converting a phosphor through a pump beam of blue or ultraviolet light. Here, the conversion of the phosphor has advantages in aspects of manufacturing cost, color temperature control, and light emitting efficiency. When the white LED is realized using the phosphor, a portion of the original blue light or UV is not absorbed into the phosphor, but is extracted to the outside. The other portion of the light is combined with the phosphor to generate color light having a longer wavelength than that of the original light.
According to related art, when a phosphor is mixed with an encapsulant to coat the mixture or a package structure is provided in which the encapsulant surrounds the phosphor, a portion of light may reenter into an LED chip because of a refractive index difference between the encapsulant and air (that is a final observation medium).
Also, because the light converted by the phosphor generates light in all directions by a self-emitting process, a portion of the light may essentially reenter into the LED chip.
A light extraction structure, which is provided on a surface of the chip to improve light extraction efficiency, may increase an amount of reentering light. Thus, the generated light may reenter into the chip to lose a portion of the light due to absorption loss within the chip. Accordingly, the light emitting efficiency may be reduced, and the reliability within the chip may be degraded.